In a medium skillet, melt butter over medium heat. Add the leeks, green onions or ramps and reduce the heat to low. Cover the pot and cook gently 5 minutes. Remove lid and stir in flour, stirring constantly to avoid lumps. Remove from heat.

While the onions are cooking, in a large sauce pot, bring stock to a low boil. Add sorrel and reduce heat so liquid is simmering. Cook until sorrel is mostly wilted, about 2 minutes, then reduce heat to medium-low, cover pot and cook 10 minutes, stirring occasionally. Uncover soup and stir in cooked onion mixture. Stir together and taste for seasoning.

In a small bowl, whisk cream and egg yolks together. Add a ¼ cup hot soup to cream mixture and whisk together. Add another ¼ cup of soup, whisk and repeat once more. Pour the hot cream mixture back into the pot of soup, continuing to whisk. Make sure soup is just below simmering and cook 5 minutes. Serve immediately garnished with sorrel pesto.

It’s the season for brighter, fresher flavors: The tangy sweetness of strawberries, the tender grassiness of just picked asparagus, the refreshing sharpness of sorrel and the spice of young garlic and onions are just what we’re longing for after the darker, heartier foods of winter. It’s an age-old craving, this desire to indulge in the tonic vegetables and fruits of …